Summary

The properties of polymers depend not only on their composition—the types of monomers used to synthesize them—but also on their topology. Differences in how polymer chains are connected within the molecule can lead to materials properties that vary for polymers made from the same monomer. For example, high-density polyethylene made with mostly linear chains and few branches is stiff and strong, and can be used for pipes. When made with many branching chains, it is more flexible and can be used in shopping bags. More complex structures can be created with copolymers containing two or more monomers that allow variations in both composition and chemical functionality. In this way, advanced materials used in health and beauty products, optoelectronic and microelectronic materials, and structural applications have been developed (1, 2). The latest challenge is to combine all of these elements—composition, topology, and functionality—into one material, and to do so in ways that reduce the complexity and cost of synthesis.